Dongle in server mode with connect needs 100-400 ms to answer Read or Write response

[jean-marc]

Using a Peripheral set in Central mode and write then read data back in the Dongle nRF5240 set in Server Mode.

Once connected and exchange MTU (extended) I write and then read my data. The read response or the write response are very long up to 400 ms for the read response.

Sending 1 byte or 240 bytes does not make any differences.

Why is this delay for?

My Interval connection is set to the minimum 7.5 ms.

Are this timing correct? Can I made then shorter?

Thank for helping.

Jean-Marc

[Edvin]

Hello Jean-Marc,

I am a little confused. Can you clear up for me whether the dongle is a central or peripheral, and what is the other device? A cellphone or another chip?

Do you use notification or indication? And which device is writing(central or peripheral), and which device is reading(peripheral or central)?

Best regards,

Edvin

[jean-marc]

Thank you...

The Nordic dongle is used as peripheral/server, I setup my server parameters and used another device as central to read/write it.

The central is a CC2640R2 and I deal without any problems with both units. The only problem is the time for a response after the writerequest or the readrequest, it is about 100-400ms and I have no idea what the dongle is doing to answer with such delay.

Is this part of the BLE that the server needs a turnaround time to answer?

Both device are close each other.

jean-marc

[Edvin]

Hello Jean-Marc,

Is it possible to provide a sniffer trace? If you have a spare nRF DK you can use the nRF Sniffer. 

Please see this blog post.

The delay that you describe seems a bit long. A sniffer log would probably tell us what the devices are waiting for.

Is this something you use to send a lot of data, or something you typically use in the start of the connection?

BR,

Edvin

[jean-marc]

I will try the Sniffer.

I am testing the throughput, because I will have to transfer a lots of data and it has to be BLE.

Thank you for the hint, I will come back if I found a solution.

[Turbo J]

Try printing  out the connection parameters, especially the connection intervall. A long connection interval could explain this behaviour.

The softdevice reports this in the BLE_GAP_EVT_CONNECTED and BLE_GAP_EVT_CONN_PARAM_UPDATE message.

[jean-marc]

Oh! OK this sounds a good verification. But I did not install any SDK for the dongle. I am just using the dongle as is with Connect to help me develop another product. I still have to figure out where to install this. Will do it.

[Edvin]

Check out out getting started guide.

I really recommend you to use the nRF52840 DK if you intend to do some development with the nRF52840 chip, as the dongle doesn't have a programming chip, so it is not possible to debug.

Also, if you intend to transfer a lot of data, you should look into notifications. It is quite common in all of our examples.

Best regards,

Edvin

[jean-marc]

Thank you everybody for your answers. You made me pinpoint the interval connection. But as I wrote I already set this to my central.

Anyway I still do not know why this happen but I interfaced with another server on Linux and used the "btmon" (I do not know how to setup the sniffer with my dongle).

I noticed on btmon that the connection interval  reported was not what I had setup on my code, neither from my central neither from my slave.

So I send the command for a "LE Remote Connection Parameter Request" and finally this updated the connection interval as set by my code.

No idea why BLE is acting like this.

Also used now notify as suggested but cannot set it to the dongle to notify :-(

[Edvin]

Hello,

If you are new to BLE, I suggest that you look into one of our examples to begin with. And if you only have the dongle, this example can be a good place to start.

You can use the nRF Connect for Mobile to trigger notifications on the service, and play around with it.

But I can't stress enough that for development purposes, a DK is a lot easier to work with, as it provides debug possibilities, which the dongle does not have. The dongle is intended as a development companion, which you can use with nRF Connect, to connect to the device that you are actually developing on.

[jean-marc]

Thank you Edwin for your answer.

I am not really new to BLE but rather for the use of Nordic.

Do you mean that I can run the linked example with the dongle nRF52840?